Variable color illuminator



Aug. 4, 1964 F. L. WAY 3,143,300

VARIABLE COLOR ILLUMINATOR Original Filed July 21. 1961 INVENTOR.FREDERICK L. WAY

ATTORNEYS- United States Patent 3,143,300 VAREABLE COLQR ILLUMKNATGRFrederick L. Way, Whitestone, N.Y., assignor to Mobilcoior, Inc, NewYork, NE. Continuation of application Ser. No. 125,854, .luiy 23, 1961.This appiieation Mar. 4, 1963, Ser. No. 263,378 9 Claims. (Cl. Eith-3.1)

This invention relates to variable color illuuminating devices and, moreparticularly, to a new and improved device which is capable of providingan illumination having wide range of hue and intensity variationsoccurring at random. This application is a continuation of my copendingapplication Serial No. 125,854, filed July 21, 1961, for Variable Colorilluminator.

In general, the presently known variable color illuminating devices haverequired complex mechanical switching arrangements operating accordingto a predetermined program which, by virtue of its constant repetition,becomes tiresome and fails to maintain the interest of an observer.Moreover, in most of the conventional variable color illuminatingdevices, each color light source is turned completely on or off at anygiven time so that the number of hues provided by the resultingillumination is restricted to that of each of the sources along withthose of the combinations two or more sources operating at fullintensity. Furthermore, with the on-off arrangement for each lightsource, the intensity of light provided by the illuminator varies inlarge steps over a range of three or four to one, depending on thenumber of light sources used, so that an observer is disturbed by thenecessity tor accommodating to the wide variations in intensity.

Accordingly, it is an object of the present invention to provide a newand improved variable color illuminator which overcomes theabove-mentioned disadvantages of presently known illurninators.

Another object of the invention is to provide a new and improvedvariable color illuminator capable of producing an almost infinitenumber of different hues and intensities of illumination.

A further object of the invention is to provide an illuminator of theabove character wherein the color variations occur at random and theintensity of illumination varies in relatively small steps.

An additional object of the invention is to provide a simple, compactand inexpensive variable color illuminating device.

These and other objects of the invention are attained by providing aplurality of electric light sources of different colors, electricalresistance means connected in series with each light source, and aplurality of thermal switch devices, each connected across a selectedportion of the resistance means to shunt out the corresponding portionwhen the thermal device closes in response to the heat generated by theresistance means. Preferably, the total resistance of the resistancemeans is just sufficient to cause the corresponding light source tooperate at a threshold level and the various portions of each resistancemeans have difierent values which are selected to provide, separatelyand in combination, a series of light intensity levels which differ byuniform intensity steps.

Patented Aug. 4, 1964 Further objects and advantages of the inventionwill be apparent from a reading of the following description inconjunction with the accompanying drawings in which:

FiG. 1 is a perspective rear View, partly broken away, illustrating atypical variable color illuminator arranged according to the invention,and

FIG. 2 is a schematic circuit diagram showing the electrical circuit ofthe present invention.

In the representative embodiment of the invention shown in the drawings,a variable color illuminator 10 comprises a reflector housing 11supported on a stand 12 wherein three electric lamps 13, 14, and 15 aremounted in sockets in the usual manner. The three lamps each provide adifierent color of light such as red, green, and blue and, to this end,they may be covered with corresponding filters 13a, 14a, and 15a (FIG.2). At the rear of the housing 11 an insulating board is supportedwithin an enclosure 17 and, mounted on the insulating board, are threeheat generating resistors 18, 19, and 20 which may be made, for example,of helically wound lengths or resistance wire such as nichrome. Mountedabove and closely adjacent to the resistor 18 are three normally openbimetallic thermal switches 21a, 22a, and 23a which are connected inshunt with selected portions of the resistor, corresponding portions ofthe resistors 19 and 20 being shunted by similar thermal switches 21b,22b, 23b and 210, 22c, 230.

An electrical cable 24 supplies power to the illuminator and, as bestseen in FIG. 2, one conductor 25 of the cable is connected to oneterminal of each of the three lamps 13, 14, and 15 while the otherconductor 26 is connected to the other terminals of the lamps throughthe resistors l8, l9, and 20, respectively Preferably, the threeportions or elements of each resistor, which are indicated in FIG. 2 byprimed, double-primed, and triple-primed reference numerals, areprovided by locating taps at selected positions along a single resistor,but, if desired, they may be separate resistors having the desiredvalues of resistance.

In order to permit a rapid response to operation of the thermal switchesand to generate suflicient heat to effect dependable actuation of theswitches, the total value of resistance connected in series with each ofthe lamps is selected to maintain the lamps at a threshold operatinglevel without producing any appreciable light intensity when all of thecorresponding thermal switches are open. It will be understood that,with incandescent lamps, the total resistance required to accomplishthis will, in general, be different for the different colored larnpsbecause of the non-uniform spectral distribution of the light from suchlamps. Furthermore, the values of resistance for the three elements ofeach resistor are selected so that the light intensity levels producedby connecting various combinations of the elements in series with thelamp differ by uniform intensity steps.

In a particular example utilizing three watt lamps and a volt powersource, the lamp 13 projected red light and the resistor 13 had a totalresistance of 245 ohms so as to provide threshold operation with thethree thermal switches open. In this case, the three elements 13, 18,and 18" had resistance values of 35, 70, and ohms, respectively. Thetotal resistance in series with the green lamp 14 was 210 ohms, dividedinto portions of 30, 60, and 120 ohms, while the blue lamp 15 r 3required 25, 50, and 100 ohm resistance elements. With thesearrangements, seven uniform resistance steps are provided for each lampby selective closing of the appropriate thermal switches. For lamps ofhigher or lower wattage than 75 watts, the resistance of each elementshould be equal to the value given above multiplied by the ratio of 75to the intended lamp wattage. It will be understood that, if necessary,the actual values of the resistance elements may be varied from thosegiven above in order to compensate for non-linear response of the lampsto changes in current so as to produce uniform light intensity steps.

Preferably, the cycles of operation of the thermal switches for eachresistor are arranged so that the large intensity variations take placeless frequently than the smaller intensity variations. To this end, thethermal switch cycles are made progressively longer for larger values ofresistance. This can be accomplished by locating the switches closer toor farther from the resistor and adjusting the spacing between thethermal element and its contact or by using thermal elements havingdiiierent characteristics. Particularly pleasing effects are obtainedwhen the time cycles for the switches shunting the smallest resistanceelements are of the order of about ten seconds and the cycles of theswitches shunting the largest resistance elements are of the order ofone minute, each switch being closed for about one-half its cycle. Othertime cycles may, of course, be provided according to the intended use ofthe illuminator.

If the enclosure 17 for the resistors is completely closed so that noair drafts can reach the resistors, the cycles of operation of thevarious switches will, after an initial warm-up period, remainsubstantially constant. In this case, the housing 11 and enclosure 17are prefer ably made of metal to conduct the heat of the resistors awayfrom the enclosure. If desired, however, the enclosure 17 may beprovided with small ventilating louvers so that air drafts passingthrough the enclosure can produce interesting variations in theswitching cycles.

In operation, electrical power is applied to the lamps 13, 14, andthrough the cable 23 and the resistors 18, 19, and respectively,initially causing each lamp to operate at a threshold level ofillumination. Heat transmitted from the various portions of theresistors causes the thermal switches to close more or less at random,shorting out the corresponding resistance elements. When each thermalswitch has cooled sufilciently, it opens to start the cycle again. Thisproduces a random variation in the intensity of the light from the lampamong several levels separated by uniform steps. In the illustratedexample each lamp, having three thermal switches, provides eightdifierent intensity levels.

Inasmuch as the hue of a color produced by mixing two different coloredlights depends on the relative intensities of the lights, it will beapparent that any two of the lamps 13, 14, and 15 can provide 64different types of illumination of varying intensity and including awide range of different hues while, with all three lamps operating, over500 different types of hue and intensity combinations can be produced.Obviously, by adding another colored lamp or an additional thermalswitch for each lamp, the number of possible hue and intensityvariations can run into the thousands. Also, because the cycle times foreach switch are seldom exactly the sane from one cycle to the next, thepattern of intensity and hue variations changes continuously.

From the foregoing it will be readily apparent that the colorilluminator of the present invention provides an almost infinite numberof different color and intensity variations occurring at random so as togenerate a continuously varying pattern of color and intensity changes.At the same time, the illuminator is simple and inexpensive in structureand operation.

Although the invention has been described herein with reference to aspecific embodiment, many modifications 4 therein will readily occur tothose skilled in the art. Accordingly, all such variations andmodifications are included within the intended scopeof the invention asdefined by the following claims.

I claim:

1. A variable color illuminator comprising a plurality of differentcolored electric light sources, resistance means connected in serieswith each light source, each of said resistance means comprising aplurality of heat producing resistance elements, and a plurality ofnormally open thermal switch means each disposed in close proximity toand connected across a corresponding resistance element, each of saidswitch means having a thermal response characteristic in conjunctionwith the heat generated by the corresponding resistance element whichdifiers from the thermal response characteristic of the other switchmeans associated with the same resistance means so that said switchmeans will close at random time intervals in direct response to heatgenerated by the element.

2. A variable color illuminator according to claim 1 wherein the valueof each resistance means is equal to the resistance required to providethreshold operation for the corresponding light source.

3. A variable color illuminator according to claim 1 wherein the valuesof the resistance elements in each resistance means are selected toprovide a plurality of light intensity levels which are separated bysubstantially uniform intensity steps.

4. A variable color illuminator according to claim 3 wherein the cycletimes for the thermal switch means connected across the larger valueresistance elements are greater than those for the thermal switch meansconnected across the smaller value resistance elements.

5. In a variable color illuminator including a plurality of socket meansfor receiving dilferent colored light sources, the combination ofresistance means connected in series with each socket means, each ofsaid resistance means comprising a plurality of heat producingresistance elements, and a plurality of normally open thermal switchmeans, each located closely adjacent to and connected across acorresponding resistance element, each of said switch means having athermal response characteristic in conjunction with the heat generatedby the corresponding resistance element which difiers from the thermalresponse characteristic of the other switch means associated with thesame resistance means so that said switch mean will close at random timeintervals in direct response to heat generated by the element.

6. A variable color illuminator comprising a housing including areflector portion and an enclosure portion, a plurality of differentcolored electric light sources removably mounted in the reflectorportion, insulating board means mounted in the enclosure portion, aplurality of heat generating resistance means mounted on the insulat- 7ing board means each connected to one of the light sources,

each of said resistance means comprising a plurality of heat producingresistance elements having different values of resistance, and aplurality of normally open thermal switch means each disposed in closeproximity to and connected across a corresponding resistance element,eachv of said switch means having a thermal response characteristic inconjunction with the heat generated by the corresponding resistanceelement which diilers from the thermal response characteristic of theother switch means associated with the same resistance mean so that saidswitch means will close at random time intervals in direct response toheat generated by the resistance element.

7. A variable color illuminator according to claim 6 wherein eachresistance means comprises a helically wound length of resistance wirehaving taps connected at selected points to divide it into resistanceelements.

8. A variable color illuminator according to claim 6 wherein theenclosure is imperforate to prevent air circulation through it.

9. In an illuminating device, an arrangement for controlling an electriclight source comprising resistance means connected in series with saidlight source, said resistance means comprising a plurality of heatproducing resistance elements, and a plurality of normally open thermalswitch means each disposed in close proximity to and connected across acorresponding resistance element, each of said switch means having athermal response characteristic in conjunction with the heat generatedby the corresponding resistance element which differs from the thermalresponse characteristic of the other switch means associated with thesame resistance means so that said switch means will close at randomtime intervals in direct response to heat generated by the element.

References Cited in the file of this patent UNITED STATES PATENTS496,474 Dillon May 2, 1893 1,402,417 Hamilton Jan. 3, 1922 1,790,903Craig Feb. 3, 1931 2,304,888 Davis Dec. 15, 1942 2,359,545 Campbell Oct.3, 1944 2,408,669 Mattson Oct. 1, 1946 2,515,236 Kunins July 18, 1950

1. A VARIABLE COLOR ILLUMINATOR COMPRISING A PLURALITY OF DIFFERENTCOLORED ELECTRIC LIGHT SOURCES, RESISTANCE MEANS CONNECTED IN SERIESWITH EACH LIGHT SOURCE, EACH OF SAID RESISTANCE MEANS COMPRISING APLURALITY OF HEAT PRODUCING RESISTANCE ELEMENTS, AND A PLURALITY OFNORMALLY OPEN THERMAL SWITCH MEANS EACH DISPOSED IN CLOSE PROXIMITY TOAND CONNECTED ACROSS A CORRESPONDING RESISTANCE ELEMENT, EACH OF SAIDSWITCH MEANS HAVING A THERMAL RESPONSE CHARACTERISTIC IN CONJUNCTIONWITH THE HEAT GENERATED BY THE CORRESPONDING RESISTANCE ELEMENT WHICHDIFFERS FROM THE THERMAL RESPONSE CHARACTERISTIC OF THE OTHER SWITCHMEANS ASSOCIATED WITH THE SAME RESISTANCE MEANS SO THAT SAID SWITCHMEANS WILL CLOSE AT RANDOM TIME INTERVALS IN DIRECT RESPONSE TO HEATGENERATED BY THE ELEMENT.